The printer using rolled paper is widely applied to the fields of the supermarkets, department stores, lottery tickets and so on, for printing customer transaction documents.
Due to heavy workload, the printing paper needs to be replaced frequently. Usually, it is necessary to prompt the user to replace the printing paper when the printing paper is near end, in order to avoid paper lack during printing.
The common way is to arrange a paper near end detection mechanism on the side wall of the paper house of the printer to detect the residual amount of the printing paper. When the paper near end detection mechanism detected that the residual amount of the printing paper is less than the predetermined value, the printer sends out alarm information for prompting the user to replace the printing paper.
The paper near end detection mechanism usually can only meet the detection of a certain residual amount of the printing paper, cannot accurately detect the state of paper exhaustion. At this moment, when receiving the information that the paper is near end, the user needs to pay attention to the consumption of the paper roll at any time. Otherwise the problem that the printing content of the ticket paper is incomplete cannot be avoided and causes unnecessary trouble for the user.
In order to improve the user's operation convenience, enable the printer accurately detect the state of the consumption of printing paper, and accurately and timely prompt the user to replace the paper, Japanese patent JP28169 provides a paper end detection method.
As shown in FIG. 1, in this solution, a paper house 1′ and a reflective sensor 5′ are arranged. The reflective sensor 5′ is slightly above the surface of the paper house. When the printing paper is near end, the paper roll becomes lighter, and the paper roll disengages from the paper house by the printing paper. At this moment, the reflective sensor 5′ detected the paper lack state, and sends out alarm information of paper exhaustion.
The disadvantage of the solution is that, as the residual amount of the paper gradually decreases, the weight of the paper roll 3′ also gradually decreases. It is easy for the paper to drag the small paper roll to roll in the paper house in the process of paper movement. When the small paper roll rolls in the paper house to be outside the detection range of the reflective sensor 5′, even if the small paper roll still has residual paper, the reflective sensor 5′ may send out a paper lack alarm, which causes an unreliable detection result.